Control of electrical discharges from electrical conductors.



W. A. SCHMIDT. CONTROL OF ELECTKICAL UISCHARGES FROM ELECTRIQM. CONDUCTOR S. APPLICAHON HLED )ULY I7. 9H

1,263,944 Patented @1223, 1918.

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Win12: flab??? W. By Jan/K \tturnuys UNITED STATES PATENT OFFICE;

WALTER AUGUSTSCHMIDT, or'Los ANGELES, qamronma, ASSIGNOR TO INT!!! NATIONAL rnncmrnrzouoomranr, or nos Antennas, CALIFORNIA, A consona'rrorr or cALrronnIA.

CONTROL OF ELECTRICAL DISCKARGES FROM ELECTRICAL CONDU'OTG'RS.

Specification of Letters Patent. I Patented Apr. 23, 19 18.

Application filed July 17, 1911. Serial No. 839,016. I

To all whom it may concern:

Be it known that I, WALTER SonMrp'r, a citizen of the United States, residing at Los Angeles, in the count of Los'A'ngeles and State of California, ave invented certain new and useful Improvements in the Control of Electrical Discharges from Electrical Conductors; and I hereby declare the following to be a clear, full, and exact description of the same.

My invention" relates broadly to electrical discharges from charged bodies such'as hi h potential conductors, and it has for its 0 ject the control and reduction of the electri cal leaka e or leakage? from such bodies, which le ages are 0 n designated as line losses or corona losses. Thephenomenon accompanying this discharge or leakage of electricity from a conductor into the surrounding atmosphere is'termed the corona,

and the voltage at which corona begins is termed the critical voltage.

It is conceded by those skilled in the art that the higher the potential at which electric energy is transmitted through conductors, the greater the efiicienc serious ditliculty encountered in indefinitelyincreasing the potential at which this electric energy is transmitted is that there exists a practical liinit for each specific conductor under specific conditions, which, if exceeded, will cause a decided increase in .the discharge of electricity into the surrounding atmosphere. p

The critical voltage determines the ex-. treme potential under which an electrical conductor may be o rated ,efiiciently; an increase in the potential will result in an increase in the electrical'leaka ge therefrom,

with an accompanyingidecrease in eificiency.

An important a p tion may befoun in its employment in high potential transmission'lines, as said invention relates particularly to methods and means to overcome, or, at least, to diminish-the corona losses, so that,- by the utilization of my said invention, a higher potential may be maintained without operating the line at a potential above the critical voltage.

To better understandmy invention, ref: erence is now made to the sheet of drawing herewith accompanied and forming a part of this specification, wherein Figure 1 is a andc be arranged in the same However, a.

cation of my inyen-' diagrammatic elevation of a device initially AUoUsT employed byme to prove the accuracy of my deductions. Figs. 2 and 3 are so atic views of devices used 1n successive steps taken to dem'onstratethe fundamentals of my invention. Fig. 4 is a diagrammatic view of a short length of a conductor'embodying m inline 0 of Fig. 2, the radial lines being understood to indicate the electric field "surrounding the conductor, and, the concentric circles, the'uni-potenti'al lines. Fig. 6 is-a cross section in lines 1 1 of Fig. 4, showing approximately the distribution of the unipotential lines in a conductor embodying the subject matter of my invention.

In the course of many experiments I found that if a conductor, such as b, Fig. 1,

which for'example ma be a pointed rod, he

charged with lailpotential beyond'its critical volta e, a b lant corona discharge b woul .take place therefrom. Next, I established the fact thatif similar conductors a lane with conductorb, on opposite sides t ercof and in close proximity theretp, all havingtheir '-points in the'same plane and being arranged perpendicularly. to a relatively large metallic plate]; and said conductors be charged to the same electrical potential to which bwasoriginally charged, thecorona discharge 1) was destroyed. In order to roduce this result, it is necessary that t e conductor I) should be in a certain zone intermediate the conductors w and c which is herein referrdto as the zone of inductive interference. I

In the extension of the above experiments I' substituted a conductor d,-placed axially within a cylinder 0, connecting one terminal of the source of electrical su ply to said flylinder a, and the otherto e conductor Similarphenomenonynamely, a brilliant corona dischar took' lace. When, however, I substitute a plur ity of conductors 1 for, thesingle conductor (1, said conductors being arallel to each otherand concentric to I and coupled them t 0 the initial source 0 invention. Fig. 5 is a section c axis of the cylinder eg v electric energy at the same potential ;as

before, said corona again was destroyed.

This phenomenon was accurately-- tested by delicate instruments under refined methods, with the result that I definitely proved in -to requirements of mech that by dividing or splittin a conductor into a plurality of paralle members 1, properly spaced and arranged, the leakage or corona losses can practically be overcome, even though the potential transmitted be above the critical voltage of ajsingle solid or stranded onductor havin a cross sec tional area equal lo- $118 combined-cross sectional areas of the several members 1 01' my so-called divided or split conductor.

My invention, based on the above described principles of action, comprises a transmission line or conductor substantial] as illustrated in Fig. 4, which shows a divided conductor consisting of a plurality of longitudinally extendin members 1, arranged iii-annular orpo ygonal-system, andextendin parallel to one another andto'the axis of t e system. Theseconductor members 1 are maintained-in properrelation by spacing disks 2, of any convenient form, insulating or non-insulating, and hold the conduetors in spaced relation, so that each is within the zone of'inductive interference from adjacent members, these-disks bei arranged at intervals along the line accord anical support.

he result obtained upon the electric field surrounding a single conductor, and,also, when a conductor is divided or split into a plurality of members 1, as described, is rou hly illustrated in Figs. 5 and 6, respective y. With a single conductor 11, as in ,Fig. 5, it'js seen that the-electric field in-'- tensity increasescontinuously up to the surface of the conductor. When the electrical potential upon the conductor 11 is raised, the

I field intensity at the surface'of the same soon reaches the critical value, .when a break downof the dielectric surrounding the 001T- ductor takes place, giving the phenomenon of corona. A aphic representation of this condition can fe shown in the continuous shortening of the concentric uni-potential lines as the surface of the conductor 4 is reached. In the case of a conductor comprising a plurality of members 1, however, as shownin Fig. 6, the uni-potential lines are not concentric to the individual members 1 of the conductor, but the reason of the inductive interference of the adjacent members or wires, tend to assume a curvature concentric with the annular or polygonal system of members or wires,'as a who e, so t at the effective convexity of the divided conductor .is approximately that of the annular or polygonal system, thus overcoming the high field intensity at the surface of any particular member 1 of said conductor, andpreventing the resultant break-down of the dielectric surrounding the conductor, such as would occur with the single conductor 03 shown in Fig.5. Thus, it is apparent that constructing aconductor with a plurality of members 1, properly arranged with respect practising my invention it may .ppenomenonw It is, therefore,

with a'hi to each other, a much higher potential can be given to that conductor before the breakdown point of the dielectric is reached, than would be possible with a conductor consisting of a single element. It is also evidert that the character of the electric field surroundinga divided ors lit conductor can be arrangement of the separate members 1 thereof.

I now direct attention to thefact that in become necessary that "my divided or split conductor be especially designedLfor each particular installation, as atmospheric conditions in the particular locality, the voltage carried, thc general" construction "of thetransmission line, together with all other local will'have a decided'eflect upon the'corona not practicae to establish any standard arrangement of the members 1, of this divided'or 'split conductor,-which will be adapted to best meet all conditions, audit is to be understood"-'that-'any *forn'r 'of divided conductor arranged soas'to meet specific conditions is within the scope of my invention.

I here state-that"a"solidtor stranded con doctor of relatively large effective cross sectional area may have a critical voltage decidedly lower than aconductor embodying this inventionain which the combined cross sectional area of its several members is less than the cross sectional area of the solider Strandedwonductor, What-I wish to emphasize is that with a plurality of members 1, properly arranged and definitely separated, it is ossible to operate my conductor er potential without reaching the critica voltage than would be possible in'the employment of a solid or stranded conductor area the equivalent to the sum of the cross sectional areas ofall the members 1 of said divided or s lit conductor.

The con uctor above described. consists wholly of conductor-elements extending lon- 'gitudmally andfparallel to the axis of the conductor as a whole so that all the metal of the conductor is fully-effective for electric current transmission, and the s acin of such conductor elements around t c axis of the conductor as a whole is such as to reduce the intensity of the electrostatic field, and resultant corona, adjacent to the conductor as a whole, to the required extent, solely b the inductive actions dueto said lon itudinally extending conductor elements, t e mechanical supports, extending transversely to the conductor as a whole, and supporting said conductor elements in such spaced relation, being only provided at the intervals required for 'such mechanical sup ort.

The subdivision of the con uctor into spaced apart elements has, in addition to the conditions,

aving an eflective cross sectional varied' et will; by' varyingthe number and i What I c reduction of corona losses, the advantage of increasing the carrying capacity for comparatively high frequencies, as it decreases the coefficient of self-induction for the conductor as a whole. The members 1 of my conductor ma be arranged in essential parallelism but elically disposed with respect to the common axis, which disposition I desire to be considered as an equivalent to the structure herein disclosed.

. Haring thus fully described my invention, aim as new and desire to secure by Letters Patent is 1. A conductor for high tension electrical current transmission consisting wholly of electrically connected conductor elements extending longitudinally and arallel to the axis of the conductor as a w ole so that all themetal of the conductor is fully effective for current transmission, and spaced apart around said axis in such relation that the field intensity and resultant corona adjacent each conductor element is reduced by induc- -tive action from adjacent .conductor elements, and supporting means for holding said conductor elements in such spaced relation, said supporting means being provided only at such intervals as are required 'for mechanical support of the conductor.

2. A conductor for high tension electrical current transmission consisting wholly of electrically connected conductor element's extending longitudinally of the axis of the conductor as a whole and arranged in a polygonal system around said axis, so that the etfective current carrying capacity of all the metal of the conductor is obtained and the corona loss from the conductor is reduced to approximately the loss from a conductor having the same cross sectional area as such polygonal system as a whole, and supporting means for holding the conductor elements in such spaced relation, said supporting means being provided only where reguired for mechanical support of the conuctor.

3. A conductor for high tension electrical current transmiwion consisting wholly of electrically connected conductor elements extending longitudinally'of the axis of the conductor as a whole and arranged in a polygonal system around said axis, so that the effective current'carrying capacity of all the metal of the conductor is obtained, ,and the corona loss .from the conductor is -reduced to approximately the loss from a conductor having the same cross sectional area as such polygonal system as a whole, and supporting means for holding the conductor elements in such spaced relation.

In witness that. I claim the fore oing I,

have hereunto subscribed my name t is 10th day of July, 1911.

' WALTER AUGUST SCHMIDT. Witnesses: LINN BRADLEY, A. A. Scam. 

